Thumbs for excavators are well known (the term “excavator” as used herein is intended to encompass excavators, backhoes, and other machines having an arm or “dipper stick” that carries a bucket or other work implement). These thumbs are secured to the arm of the excavator and are arranged relative to the bucket or other work implement so as to provide an opposable member to aid in grasping large or odd-shaped objects and/or for other purposes. The thumb includes a body having an inner end secured to the excavator arm and an outer end that is spaced outwardly from the arm. The outer end can have any of a wide variety of shapes and sizes, depending upon the work being performed, e.g., carrying logs, carrying demolition debris, lifting large rocks or metal plates, and similar activities.
Known thumbs are either a fixed or “stiff-arm” type that is set to a desired operative position, or a continuously remotely adjustable “hydraulic” type in which the angular position of the thumb body relative to the excavator arm is selectively continuously adjustable using a remotely controlled hydraulic cylinder or other actuator controlled by the machine operator from the operator's cab. These known thumbs cannot be quickly and conveniently changed from one type to the other once installed on an excavator, because the stiff-arm thumb requires a different base mounting structure to be installed on the excavator arm as compared to a hydraulic thumb.